Slurry Pump Seal Leakage

The repeat failure of the new P-105 slurry pump has caused repeat, unplanned shutdowns resulting in lost profit and excessive expenditures due to seal leaks. The slurry contains 50% methyl bad stuff which is an environmentally regulated chemical and requires the pump to be shut down upon detection of a leak greater than 2kg/hr causing production losses amounting to $240,000 thus far. These losses will increase as product demand grows.The project team was under cost- and timing- pressure, and specified a seal that was not suitable for this service. In order to prevent repeat seal failures, the corrective action is to install a new type of seal and stuffing box capable of handling the solids. The preventive actions are to integrate a reliability review with all new capital projects and to require the area reliabilty engineer to provide design criteria to the project teams for special, known process and equipment requirements.

The unplanned shutdown was caused by a seal leak of slurry pump P-105. The seal leak was the result of a single mechanical seal being installed in slurry service. Single mechanical seals with discharge recirc flushes in slurry service fail due to solids depositing on the seal faces. Deposits open the seal faces as the pumped liquid evaporates across the seal faces, leaving solids behind. This opens the seal faces creating increasingly worse seal leakage. The single mechanical seal was installed because the project team didn't know it was not the best choice, and because it was inexpensive. The team didn't know it wasn't the best choice because they didn't seek reliability input and because no one gave them input upfront as to the most effective design criteria for the process and equipment requirements. The missing input was caused by no step, or requirement, in the capital project guidelines to integrate reliability input. The project team also went with the single seal because they were looking to cut costs due to budget contraints imposed on them by the business and because they were projected to be over budget. They were also in a rush to complete the project in order to get the product to market more quickly.

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